Augmented Reality (AR) is a technique which computes in real time a camera's position and direction and provides corresponding images. This technique is aimed to combine the virtual world with the actual world. It has been used more and more widely with the improvement of the computing capacity of electronic devices. Virtual Reality (VR) is a computer simulation system capable of creating and experiencing the virtual world, which uses a computer to generate a simulative environment. VR is a multi-source information fusion and interactive system which combines the three-dimension vision with a physical behavior, so that a user may immerse himself in the environment.
In most cases, when the augmented reality device and the virtual reality device are placed on the user's head, the user may not see the environment behind or the environment outside the device. When the user is in movement, for example, the user takes a standing and walking posture, and if there is an obstacle around, e.g., a building wall, safety problems may occur. Besides, sometimes in a scene where the user interacts with others or the contents in the virtual reality/augmented reality system, the user may need to achieve a certain action or to intervene in the user's actions, for instance to implicitly make the user turn around or to walk along an arc, so as to reach the goal of the application or the game. These effects cannot be achieved by current technologies.